Load stabilized crane



Sept. 10, 1957 l A. sENN 2,805,78

LOAD STABILIZED CRANE:

Filed Jan. 24, 1955 6 Sheets-Sheet l A rroeA/EV lSept. 10, 1957 A; L. sENN 2,805,781

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y LOAD STABILIZED CRANE Filed Jan. 24, 1955 6 Sheets-Sheet 3 ATTO/@N57 Sept. 10, 1957 A. l.. SENN 2,805,781

LOAD STABILIZED CRANE Filed Jan. 24, 1955 e sheets-sheet 4 'INI/ENTOR.' AEN/0,2 L. S15/VN ISeptQlO, 1957 A. L. sENN 2,805,781

l LOAD STABILIZED CRANE Filed Jan. 24, 1955 5 sheets-sheet 5 INVENTOR. Agn/ue z.. s'EN/v Sept. 10, 1957 A. sr-:NN 2,805,781

LOAD STABILIZED CRANE Filed Jan. 24, 1955 6 Sheets-Sheet 6 INVENTcm Agn/UQ L sav/v ,4 r roem/EV Unite States Patent fi LOAD STABlLIZED CRANE Arthur L. Senn, Seattle, Wash.

Application January 24, 1955, Serial No. 483,681

Claims. (Cl. 212-58) This invention relates to cranes of the class particularly adapted for use aboardL ships, although they also may be used to advantage for mobile or stationary installations, such as on land, wharfs, or docks.

-Since in many ports ship loadingiacilities are inadequate or even non-existent, it is desirable to provide on the ships themselves suitable cranes for loading and unloading cargo from and to docks and lighters. However, the operation of shipboard cranes is attended by serious difficulties in that the ships on which the cranes are mounted are not stationary, but roll and pitch with wave motion and list with change in cargo position. As a consequence, it is dicult to handle loads aboard ships with conventional type cranes, due to unstable conditions, and conventional cranes under such conditions expose the cargo handlers to grave hazards.

Accordingly it is a general object of the present invention to provide a single load fall crane with a load stabilization mechanism and which crane may be mounted and used on a ship safely and effectively, and which is characterized by the following advantages:

The load which it carries can be stabilized in all directions to compensate for objectionable swinging due to rotating and lufng of the crane boom or the rolling, pitching, or listing of the ship, lthereby dampening pendulum motion induced by said conditions.

Its load can be stabilized eiectively, using a minimum of supporting structure, boom structure and rigging resulting in an economical structure of improved appearance.

Its load is stabilized during all movements of the boom and hook, i. e. during all hoisting, luing and slewing operations.

The Width of the boom structure at its tip end portion is adjustable for operation at locations where the working space is limited, as alongsidel buildings, or the superstructures of ships.

Due to its stabilizing features, it can be operated rapidly and safely to handle maximum cargo in minimum time, the cargo handleable in a given time being substantially greater than that which may be handled in the same time by a conventional type crane. v

When not in use, the crane boom and its laterally extending arms may be stowed away neatly in a minimun space on the ship deck providing for eiliciency and appearance.

Other objects and advantages of my invention will become apparent as the description of the same proceeds and the invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawings forming a part of the speciiication, with the understanding, however, that the invention is not to be limited to the exact details of construction shown and described since obvious modiications will occur to a person skilled in this art.

Figure l is a view in side elevation of the herein described crane;

Fig. 2 is a plan view of the crane of Fig. l and taken substantially on broken line 2,-2 of Fig. 1;

Patented Sept. 10, 1957 ICC Fig. 3 is a plan view taken substantially along broken line 3-3 of Fig. l and illustrating particularly the control cab and the drive for the load stabilizing means;

Fig. 4 is a plan view taken substantially along broken line 4-4 of Fig. l and illustrating particularly the machine deck and the hoisting and lui-ling mechanism mounted thereon;

Fig. 5 is a fragmentary perspective view of the out-r board portion of the crane boom and depending cables;

Fig. 6 is a detail view in side elevation of the boom hook assembly; p

Fig. 7 is a detail view of the mechanism of Fig. 6 and taken at right angles to that of Fig. 6;

Fig. 8 is a detail schematic view illustrating the manner of rigging the load fall;

Fig. 9 is a detail schematic view illustrating the manner of rigging the luling and stabilizing lines;

Fig. l0 is a detail view in plan, partly in section, illustrating one form `of compensating tensioning means and braking means for the load stabilizing lines; and

Fig. 1l is a view in elevation illustrating another form of compensating tensioning means and braking means for the load stabilizing lines.

Generally stated, the presently described crane comprises a mast and a boom mounted on a supporting structure or base for slewing about a vertical axis. The boom is hinged for luing movement relative to the mast. Drive means are provided for slewing it in the usual manner.

A cargo hook is connected to the boom through means for raising it and lowering it as required to handle the cargo. Associated with the cargo hook are a pair of load stabilizing lines which pass in an upwardly diverging manner over spaced apart sheaves carried by the boom or preferably by arms extending laterally from the boom and spaced longitudinally from the boom tip, as rearwardly, to secure an effective triangulation. The arms are preferably hinged to the boom so that they may be moved between extended, intermediate and folded positions relative to the boom and lock or fixed in any of these positions.

Compensating-tensioning means are used in conjunction with the stabilizing lines for applying to them a continuous force which keeps them taut regardless of the movement of the cargo hook. In addition, brake means for the compensating-tensioning means are provided so that the degree of applied tension may be varied by the operator as desired for retarding pendulum motion or undesired swinging movement of the load. Braking means also are provided in conjunction with the hoisting, slewing and luing drives. As a consequence, precise control of the load is provided at all times.

A. THE CRANE STRUCTURE As is illustrated particularly in Fig. l, the crane of-the present invention is adapted to be mounted at a suitable station, for example adjacent a hatch, on the deck 20 of a ship. If desired for rapid loading and unloading two to four lof the cranes may be installed at the corners of each hatch.

The crane includes a base 22 upon which is rotatably mounted a housing 24, on top of which is a machine deck 26. Machinery, not illustrated, is contained within the housing 24 for rotating it about the base 22, thereby slewing the crane boom carried by housing 24.

A crane mast is attached to deck 26. It may comu prise a pair of upwardly converging structural members 28, 30, braced by cross members 32, 34. These members in turn support the operators cab 36 and boom bumpers 38, 40.

The `boom assembily includes the laterally spaced apart, outwardly converging b-oom members 42, 44 and cross pieces 46, 47. Cross piece 46 is adapted to eugage bumpers 38,y 40 when the boom is in its uppermost position.

The heels of the boom members 42, 44 are hinged to a pair of spaced apart` brackets 48,` 50 mounted on machine deck 26. The outboard or` tip end portions of boom members 42, 44 carry laterally extending arms 52, 54. These are attached to the respective boom members bymeans of hinges 56, 58 and extend upwardly with respect to the boom so that the outer ends of the arms lie in an elevated plane above a line passing through the load fall sheaves at the boom tip and the heel brackets 48, 50.

The arms 52, 54 thus, are movable between extended, intermediate and folded positions indicated at E, I, F in Fig. in conjunction with arm 54. They may be maintained in the selected position by means of telescopic stays 60, 62, the telescoping sections of which may be interlocked releasably by means of pins 64, 66 or other suitable means.

B. THE HOISTING UNIT l. The driveV The presently describedcrane lifts its load through a single load fall or hoisting cable operated from a winch centrally located on the machine deck. As is indicated in Fig. 4, the winch includes a drum 70 attached to a shaft which is rotatably mounted on pedestals, one ofV whichis indicated at 72. Drum 70 is .provided with a brake 74 and is driven through gear box 76 from motor 78 which preferably is a hydraulic motor. Another brake 80 is provided for automatically arresting the motion of the drum when the drum control is in neutral posltlon.

The operation of drum 70 is. controlled from cab 36 (Fig. 3). The motor 78, which controls the speed of rotation of the drum 70, is operated through lever 82 in the control cab. Brake 74, which is employed to deceleratethe motion'of the drum 70 when this is desirable or necessary, is controlled through brake pedal 84 (Fig. 3). Then, as has been indicated above, when motor control lever82is in its neutral position, the entire assembly is locked automatically by brake 80. In

this manner precise control of the hoisting mechanism is` achieved.

2. The rigging Drum 70- carries the load fall 90 and said Iload fall l 90 is reeved about sheaves on the mast and boom in such a manner as to achieve level lutiing of therz cargo hook (Fig. 8). Accordingly, the load fall passes over a first sheave 92 (Fig. 8) rotatably mounted on a shaft 94 (Fig. ,2) at thetop of the mast, then about a second sheave 96 (Fig. 8) rotatably mounted'forwardly on the boom, thenabout a third sheave 98 rotatably mounted on shaft 94 but spaced apart from sheave 92, and then about sheave 100 rotatably mounted at the extreme tip of the boom. The load fall 90 then extends downwardly and its terminal portion is connected through a swivel, indicated generally as 102, and a weighted connector, indicated generally as 104, to hook 106., Accordingly it will be apparent that actuation of drum 70 by control 82 will raise or lower hook 106 relative to the tip `of the boom.` Also, as the boom is luted, drum` 70 remaining stationary, the .level of hook' 106 will be maintained substantially constant.` Y

C. THE 'LUFFING `UNIT 1. The'drve The drive for the lufting unit, by which `the boom is topped and lowered, is illustrated particularly in Fig.

4. It comprises a pair of drums attached to shafts ro-V The lufiing drive is controlled from cab 36 by the controls indicated in Fig. 3. The motor 140 and drums 130, 132 are actuated by means of control lever 144 moved in a direction parallel to the longitudinal axis of the boom. Brake 142 is automatically set when control lever 144 is in neutral position. Precise control of the lulng unit is obtained through the controls illustrated and described.

2. The rigging Lutiing cables 150, 152 are carried, respectively, on drums 130, `132 and are rigged in the manner illustrated in Fig. 9. The cable is reeved about sheaves 154 and 156, rotatably mounted on shaft 158 at the top of the mast and about sheave 160 rotatably mounted on shaft 162 at the forward portion of the boom. Thus the order of reeving is about sheave 154, about sheave 160, and about sheave 156.

Similarly, cable 152 is reeved about sheaves 164, 166 rotatably mounted on shaft 168 at the top of the mast, and about sheave 170 rotatably mounted on shaft 162 located at the forward portion of the boom. Both cables 150, 152 are dead-ended and pivotally to shaft 162 as by beckets 163 and 165 respectively, which are located adjacent the boom tip. Accordingly, the boom may be lufed as desired by `suitable manipulation of the control 144 for drums 130, 132.

D. THE STABILIZING UNIT l. The drive Generally stated, the preferred. unit employed for stabilizing the load carried by hook 106 comprises a two line, double drum compensating-tensioning means for receiving two stabilizing cables `connected to opposite sides of the hook assembly and having the primary function of stabilizing the load connected to hook 106. The stabilizing unit is mounted in a convenient location, for example in an intermediate position on the mast, adjacent to andisupported by cross members 32, 34. It includes (Figs.` 3 and l0) drums 172, 174 with associated brakes 176, 178. The drums are connected to a drive shaft 182 through gearing of stabilizing unit 180, to be described in detail hereinafter.

A `brake 184 is operative upon shaft 182, its braking force being operatively greater with respect to drums 172, 174 than the combined braking forces of brakes 176, 178 with'respect to the drums 172, 174. The unit is driven by a torque motor 186, preferably hydraulic, whichiis connected to drive shaft 182 and which, when energized, runs` at a speed suicient to eliminate slack in the stabilizing cables and applies a continuous ten sioning torque to drums 172, 174 to eliminate said slack.

The stabilizing unit is controlled from the operators cab 36 (Fig. 3). Control lever 187 energizes motor 186 and which motor 186 transmits torque to drums `172, 174. Brake pedal 'actuates brakes 178, 176, and 184 hydraulically through conduit conditions 175a, 175b, and 175C. The said brakes are used to apply a braking force to drums 172, 174 and to thereby restrain the compensating or rotational `movement induced in drums 172, 174 through the stabilizing cables 188, 190 when the load hook 106 and the load suspended therefrom tends to'swing relatively to the boom tip portion.

Control lever 187 may be manually operated to energize or deenergize motor 186. In order to facilitate the lowering of a light hook 106 and minimize the weight of weighted connector 104, lever 82 may also function to lessen the torque of motor 186 when a light hook 106 is being lowered.

2. The rigging The manner of rigging stabilizing lines 188, 190 carried by drums 172, 174 is particularly apparent from Figs. 1, 6 and 9. Thus line 188 passes over rear sheave `192 asomar mounted on shaft 158 and over forward sheave 194'which swivels at the extremity of arm 52. Its outer end then is connected to swivel eye 124 on collar 120 of the hook assembly. In a similar manner, line 190 is reeved over rear sheave 196 mounted on shaft 168, and over forward sheave 198 swiveled to the outer extremity of arm 54 on the other side of the boom assembly. The outer end of the line then is connected to swivel eye 126 on collar 120 of the hook assembly.

It is to vbe noted particularly that stabilizing line sheaves 194, 198, mounted on the forward portion of the boo-m, are located a substantial distance behind forward load fall sheave 100. Also, sheaves 194, 198 are elevated substantially above a line passing through the boom tip and heel portions. This has two consequences.

In the iirstV place, it gives the desired triangulation for stabilizing the hook, as is apparent particularly from Fig. 5. Secondly, it preserves and substantially maintains this stabilizing relation in all positions of the boom. Thus even when the boom is topped and load fall 90 is relatively close to the mast, there is a sutlicient spread between the load fall and the stabilizing lines to provide the desired degree of triangulation. Accordingly, the hook may be stabilized in all positions of the boom relative to the mast.

3. T he compensating-tensioning means As has been indicated above, means are employed for keeping stabilizing cables 188, 190 under a desired tension. As a result, when swinging of the hook occurs and one of the lines tends to go slack, the slack is immediately taken up, and a tension is maintained in both stabilizing cables which dampens objectionable swinging or pendulum motion of the crane hook. A preferred compensatingtensioning means is illustrated in Fig. 10.

In accordance with this embodiment, drums 172, 174 which carry the stabilizing lines are mounted, respectively, on and driven through shafts 200, 202. These, in turn, are driven independently of each other from shaft 182 acting through the differential gearing indicated generally at 204. Since motor 186 applies a continuous tensioning torque to shaft 182, when energized, this tensioning force will be transmitted to drums 172, 174 and hence to stabilizing -lines 188, 190. Accordingly, as soon as slack attempts to appear in one of the lines and the tension therein decreases, due to swinging of the load with respect to the boom tip portion, the differential gearing acts immediately to accelerate the rate of rotation of the corresponding drum, maintaining the line involved under tension. In this manner cables 188, 190 are kept taut ready for `applying braking forces of the stabilizing unit to the hook 106 and the desired stabilizing-tensioning eifect is obtained.

The amount of tension applied -to the stabilizing lines may vary accordi-ng to the particular application. However, in general, the tension is kept at a value sufficiently low so that a force never will be applied to hook 106 by the stabilizing lines which is sufficient to lift or prevent y lowering of the hook, even though it carries no load. As previously indicated, torque of motor 186 may be lessened, if desired, during lowering of a light hook. In other words, lines 188, 190 serve a stabilizing function only and never serve as hoist lines. This is an important feature of the present invention since the stabilizing lines do not interfere with the motion of the hook, which may be raised or lowered with facilityregardless of whether it is heavy or light.

It should be observed further that the action of the stabilizing lines, coupled with the action of brakes 176, 178 and 184 is such as to give certain control over the load at all times. Thus the stabilizing lines inhibit the pendulum motion of the hook, and, being continually in a taut condition, make possible an extremely sensitive braking action. With the cables always taut, even a slight application of the brakes will cause an instantaneous a response in the travel of the hook. Hence the load is maintained continuously under precise control.

4. Universal connection for stabilizing cables Since a standard metallic Aload fall tends to twist when a load is picked up, proper means are provided for attaching the stabilizing cables to the load fall and hook assembly in such a manner that universal movements obtain. An exemplary construction for this purpose is illustrated in detail in Figs. 6 and 7.

In this construction, load fall is connected to a swivel 102 which includes a housing 108 in which are rotatably mounted au upper swivel member 110, to which load fall 90 is attached, and a lower swivel member 112, to which weighted connector 104 is attached. Ball bearing assemblies 114, 116 are provided for insuring the free rotation of the swivel members 110, 112.

The underside of the swivel housing is recessed to accommodate a ball bearing assembly 118. This in turn bears against .a collar 120 which is provided with a bearing assembly 122 and which turns freely about the shank of swivel member 112. Collar 120 'has a pair of `spaced apart, laterally extending swivel eye connectors 124, 126 to which are attached the stabilizing cables functioning ina manner described below.

Hence it will be apparent lthat load fall 90 can twist independently of weighted member 104 or hook 106. Also hook 106 and weighted member 104 can turn about ytheir vertical axes independently of load fall 90. In addition, any twisting of either of these two members will not cause objectionable twisting of the stabilizing cables attached to collar 120. It is further apparent that the universal connection formed by collar 120 and swivel eye connectors 124, 126 will permit the stabilizing cables 188, to `align themselves with their laterally spaced guide sheaves 194, v198 on the boom regardless of the vertical or lateral lrelation of the crane hook assembly with respect to the crane boom. Different positions which the stabilizing cables may assume are depicted by full and dash lines in Figs. 6 and 7.

5. Alternate compensating-tensioning means Alternate means for maintaining cables 188 and 190 under a continuous stabilizing tension are illustrated in Fig. 1l. In this embodiment the stabilizing eiect of an equalizing bar, rather than of differential gearing, is applied to keeping the cables taut under conditions of load swing relative to the boom tipportion. The weight of the equalizing bar assembly with its sheaves, sleeve and braking mechanism and the travel or movement of this assembly on post 210 provides the means for tak-ing up any slack and providing' the desired tension in the stabilizing cables 188, 190. The equalizing bar assembly m-ay be mounted in any suitable location, for example on a post 210 attached to machine deck 26 just behind the vertical mast member 28. The stabilizing lines 188, 190 pass `over sheaves 212, 214 which correspond in function yand location to sheaves 192, 196 of the previously described embodiment, the rigging forwardly of these sheaves being the same as that described hereinabove.

After passing over sheaves 212, 214, the cables pass over sheaves 216, 218, respectively, on equalizing bar 220. Thence over sheaves 222, 224, respectively, mounted on the mast frame. They then pass downwardly and are dead-ended on beckets 226, 228, respectively, attached to the extremities of equalizing bar 220. The bar, in turn, is pivotally attached through pin 230 to a sleeve 232 slidable on post 210.

Brake means are provided for damping the angular movement of equalizing bar 220 and for inhibiting its travel along post 210. The brake means employed for the former purpose comprise a pair of hydraulic cylinders 234, 236 having piston rods 238, 240, respectively, gpivotally connected to brackets 242, 244. The latter are connected to a brake member 246 mounted upon or attached to sleeve 232 and` acting to brake its motion rela-g tive to post 210..

It will be apparent that angular movement of stabilizing bar 220 will he limited by ythe rate at'whichuid-in cylinders 234, 236 can by-pass the pistons in the cylinders, this being controllable from the operators cab through control lines 248, 250.

Similarly, the rate of travel of the stabilizing bar longitudinally with respect to post 210 will be determined by the pressure applied to brake 246, this in turn being con trolled through line 252 extending to the operators cab. The braking action in this embodiment thus is strictly analogous to that illustrated in the embodiment of Fig. 10, brakes 176, 178 of the latter ligure corresponding to brake cylinders 234, 236 of Fig. 11, and brake 184 of Fig.- 10 being analogous nits effect to brake 246 of Fig. 1l.

E. OPERATION The operation of ,the herein described crane is as follows:

The operator sitting in cab 36 on the mast can control all Jof the various working motions of the cranewith controls readily available to him.` Thus lateral movement of control lever 144 causes slewing of the crane about the base 22. Actuation of lever 82 controls the hoist motor 78, forraising or lowering hook 106. Control lever 82 may also be employed, if desired, to reduce the tensioning torque of motor 186 of the stabilizing unit `during the period of the lowering a light hook 106. Further control of the hoisting action is obtained by use of brake pedal 84 whichoperates brake 74 on the hoisting unit. Furthermore, when control 82 is in neutral position, brake 80 is set automatically to render the unit inactive until further raising or lowering of the load is desired.

The boom is luled by longitudinal shifting of control lever 144. This actuates motor 140 which in turn drives drums 130, 132 carrying luing lines 150, 152. The motion of the boom is further` controlled through the. use f brake 142 which automatically sets when control lever 144 is in neutral position, longitudinally.

Throughout all operations of the crane, the load carried by hook 106 is stabilized by its friction inherent in movement of the stabilizing vunit rigging and particularly by the action of stabilizing lines 188, 190. A slight tension is applied to these lines 188, 190 by torque motor 186 operating through differential gear assembly 204. The action of the latter assembly is such that when one of the stabilizing lines lengthens, due to the swinging of the load carried by hook106 or listing of the ship, the other line will be taken up immediately by its associated drum. However, when the load is lowered, additional'line will be drawn out against the torque exerted by motor 186.

Lines 188, 190 thus are maintained under tension at all times when a load is supported by the hook. However, the amount of tension thus applied is not suticient to raise the hook even when it does not carry a load. As a .consequence, the hook may be raised and lowered by means of hoisting line 90 with facility regardless of whether the hook is `heavy or light.

Maintaining the lines 188, 190 under tension has the further desirable effect of making possible the application of an effective braking action to the stabilizing lines through actuation of brake pedal 185. This operates brakes 176, 178 and 184 associated with the stabilizing unit, controlling `the freedom with which the stabilizing lines'pay out, and accordingly enables the application of force as required to stabilize the pendulum motion of the load.

The stabilizing action of lines 188, 190 is particularly effective because of the manner in which theyare mounted as sheaves 194, 198, mounted forwardly on the boom and carrying the lines, are spaced apart by means of` arms 52, 54. Also, they are mounted longitudinally of lsheave 100 carrying the hoisting cable. As a result, .an elective triangulation of the three lines is obtained. The broad .tri-

angulation base is maintained, irrespective of whether the boom is lowered or raised. This is a result, in part, of locating stabilizing sheaves 194, 198 at the tip of arms 52, 54, which lie above a line passing through the tip and v heel portions of the boom.

Still further, establishing a broad stabilizing base by means of arms 52, 54 does not interfere with the liexibility of application of the crane to cramped environments. For example, if it is necessary to use the crane close to a warehouse on a wharf, or closely adjacent the superstructure of a ship, one or the other of arms 52, 54 maybe folded alongside the boom, or 'used in an intermediate position by adjustment of the telescoping stays 60, 62, the telescoping parts of which are held releasably interlocked by pins 64, 66 respectively. This arm-adjusting assembly may be used to advantage also when the crane is to be stowed, so that it requires a minimum of storage space.

Thus it will be apparent that by the present invention l have provided a crane uniquely suited for use as a shipboard crane, which may be mounted on a ship adjacent the hatches, thereby making possible loading and` unloading the ship with speed and ysafety even in ports where the dock facilities are lacking or inadequate. The crane is particularly suitable for such use because of the precision with which it may be controlled and because of the means which are provided for effectively stabilizing the load hook in all directions and in all positions of the boom. The crane accordingly may be used efficiently regardless of ship motion or listing. Also, it may be controlled posi tively, its working area is large, it is applicable in locations where working space is limited, and when not in use it may be stowed away, with good appearance, in minimum space.

It is to be understood that the forms of my invention, herewith shown and described, are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

I claim: Y

l. In crane mechanisms, a supporting structure; a boom structure having its heel portion pivotally connected to the supporting ,structure and having laterally spaced sheave supporting members at its tip end portion; hoist sheave means carried by the tip end portion of the boom structure and longitudinally spaced on the boom structure relative to the position ,.of the laterally spaced sheave supporting members and disposed laterally between said laterally spaced shcave supporting members;

n a hoist cable prime mover; hoist cable means for raising and lowering a load suspendedly supported thereby, the hoist cable means being engaged with the hoist cable prime mover, passing over the hoist sheave means and depending therefrom; a load-engaging means connected with the hoist cable means; laterally spaced apart stabilizing sheave means carried by the laterally spaced sheave supporting members and located above a line passing through the hoist sheave means at the tipof the boom and the pivot at the heel portionof the boom; cable tensioning means of insuliicient magnitude to lift the load-engaging means and permitting the load-engaging `means suspended from the hoist cable means to `descend by gravity; and stabilizing cable means connected with the cable tensioning means, reeved over the laterally spaced apart stabilizing sheave means and extending directly convergingly downwardly toward and connected 'withthe load-engaging means.

2. In crane mechanisms, asupporting structure; a boom structure having its heel portion pivotally connected to the supporting structure and having laterally spaced sheave supporting members at its tip end portion; hoist sheave means carried by the tip end portion of the boom struc ture and longitudinally spaced on the boom structure relative to the i position of `the laterally spaced sheave supporting members and disposed laterally between said laterally spaced sheave supporting members; a hoist cable prime mover; hoist cable means for raising and lowering a load suspendedly supported thereby, the hoist cable means being engaged with the hoist cable prime mover, passing over the hoist sheave means and depending therefrom; a load-engaging means connected with the hoist cable means; laterally spaced apart stabilizing sheave means carried by the laterally spaced sheave supporting members; cable tensioning means of insuticient magnitude to lift the load-engaging means and permitting the load-engaging means suspended from the hoist cable means to descend by gravity; stabilizing cable means connected with the cable tensioning means, reeved over the laterally spaced apart stabilizing sheave means and extending convergingly downwardly toward and connected with the load engaging means; and brake means operatively associated with the cable tensioning means for varying the magnitude of the tension in the stabilizing cable means as the load-engaging means moves in a direction as to cause lengthening of the stabilizing cable means.

3. In crane mechanisms, a supporting structure; a boom structure having its heel portion pivotally connected to the supporting structure; laterally extending arm means carried by the outer end portion of the boom structure; means for adjusting the degree of lateral extension of the laterally extending arm means; hoist sheave means carried by the outer end portion of the boom structure and longitudinally spaced on the boom structure relative to the position of the laterally extending arm means thereon; a hoist cable prime mover; hoist cable means for raising and lowering a load suspendedly supported thereby, the hoist cable means being engaged with the hoist cable prime mover, passing over the hoist sheave means and depending therefrom; a load-engaging means attached to the hoist cable means; laterally spaced apart stabilizing sheave means carried by the laterally extending arm means; cable tensioning means of insufcient magnituderto lift the load-engaging means and permitting the load-engaging means suspended from the hoist cable means to descend by gravity; and stabilizing cable means connected with the cable tensioning means, reeved over the laterally spaced apart stabilizing sheave means and extending convergingly downwardly to and connected with the load-engaging means.

4. The crane of claim 3 wherein the means for adjusting the degree of extension of the laterally extending arm means comprise telescoping stays interconnecting the arm means and the boom structure, and means for releasably interlocking the telescoping sections of the stays in predetermined positions relative to each other.

5. In crane mechanisms, a supporting structure; a boom structure having its heel portion pivotally connected to the supporting structure; laterally extending arm means carried by the outer end portion of the boom structure, said arms extending laterally of said boom structure; hoist sheave means carried by the outer end portion of the boom structure and longitudinally spaced on the boom structure relative to the position of the laterally extending arm means thereon; a hoist cable prime mover; hoist cable means for raising and lowering a load suspendedly supported thereby, the hoist cable means being engaged with the hoist cable prime mover, passing over the hoist sheave means and depending therefrom; a load engaging means attached to the hoist cable means; laterally spaced apart stabilizing sheave means carried by the laterally extending arms and positioned laterally of the boom structure; cable tensioning means of insucient magnitude to lift the load-engaging means and permitting the loadengaging means suspended from the hoist cable means to descend by gravity; and stabilizing cable means connected with the cable tensioning means, reeved over the laterally spaced apart stabilizing sheave means and extending convergingly downwardly toward and connected with the load-engaging means.

References Cited in the lile of this patent UNITED STATES PATENTS 1,228,344 Miller et al.v May 29, 1917 2,166,479 Ruddock July 18, 1939 2,625,005 Myers Jan. 13, 1953 2,627,984 Senn et al Feb. 10, 1953 2,709,526 Hansen May 31, 1955 

